Why does the binding not want to work in this case?

Question

WPF

Here is the xml:

<TextBlock FontSize="{Binding TreeViewTextSize}" Text="{Binding Title}" Margin="0 0 10 4"/>

In general, I set the value of TreeViewTextSize in the text field, it changes (checked), but it does not change in the font size of the text block, but if you put the number manually, then everything will change safely.
What is the problem?

Answer 1

1. The TreeViewTextSize property must be of type Double
2. When it changes, the view needs to be informed about it, i.e. implement the INotifyPropertyChanged interface and call PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("TreeViewTextSize"));